A Chinese national flag flutters between PetroChina's flags at headquarters in Beijing. Photo: Reuters

The state-owned oil and gas giant once run by former Communist Party leader Zhou Yongkang has pledged to maintain stability despite a government corruption probe into four of its senior executives.

The piece was published on the day the South China Morning Post exclusively confirmed that Zhou Yongkang was himself under investigation over alleged graft.

A report by China Petroleum Daily, a China National Petroleum Corporation company publication, on Friday shows how deeply the investigations have shaken the conglomerate. Over the last week, 16,300 staff members have been briefed on instructions from the party leaders in Beijing, the report, also released on the company’s website on Thursday, said.

“In the current extraordinary times, it is the explicit wish of the comrades in the central leadership to guarantee the overall stability of the company,” the report quoted CNPC chairman Zhou Jiping telling a video-conference of senior executives on Wednesday.

“All work units and leaders at all levels should ensure […] the absence of chaos in the ranks and that drilling areas are harmonious, so that the party’s central leadership and the state council can put their minds to rest,” Zhou said.

“The focus is on strengthening the supervision of cadres in leadership positions - especially leading executives,” he said. The company should “seriously explore effective ways to ‘lock powers into the system’s cage’,” added Zhou.

The meeting comes a day after CNPC said that four leading executives had resigned for personal reasons and after investigators independently announced the investigation.

The party’s Central Discipline Inspection Commission, a corruption watchdog, said on Tuesday it was investigating the company’s deputy general manager Wang Yongchun over allegations of corruption. Wang, an alternate member of the 18th Communist Party Central Committee, was in charge of the Daqing oilfield.

The following day, the State Council’s State-owned Assets Supervision and Administration Commission said it was investigating three more executives: Li Hualin, Ran Xinquan and Wang Daofu. Although it did not specify the nature of the allegations made against them.

Li was promoted to general manager last month, Caixin reported. Ran, also a deputy general manager, ran the Changqing oil fields in Western China. Wang worked as chief geologist for PetroChina, which is CNPC’s listed subsidiary.

Observers were quick to link their sacking to an ongoing corruption probe into the company’s former general manager and party secretary Zhou Yongkang. Earlier this month, President Xi Jinping asked investigators to probe the former Politburo Standing Committee member and close ally of disgraced Chongqing Party Secretary Bo Xilai. It is the highest-profile investigation launched in China in recent years.

The company received instructions on Monday, the China Petroleum Daily report said, but it did not elaborate.